Apparatus and method for digital content concealment in a storage medium recorded using a recording device

ABSTRACT

A system and process for the concealment of digital content recorded on a storage medium such as a compact disc (CD) and, more specifically, to an apparatus and method for recording a CD or other storage medium using a recording drive, such as a CD-R or CD-RW drive, that is connected to a computer and that conceals the stored digital content on the medium from being read by a compact disc read-only memory (CD-ROM) or other digital-based reader or computer device, for example as done when performing digital audio extraction (also known as ripping) of musical content from an audio CD. The apparatus and method permit improved control of the usage and copying of published content on physical media by an immediate purchaser while limiting copying and distribution of the content to unauthorized recipients.

BACKGROUND OF THE INVENTION

This invention relates in general to the concealment of digital contentrecorded on a storage medium such as a compact disc (CD) and, morespecifically, to an apparatus and method for recording a CD or otherstorage medium using a recording drive, such as a CD-R or CD-RW drive,that is connected to a computer and that conceals the stored digitalcontent on the medium from being read by a compact disc read-only memory(CD-ROM) or other digital-based reader or computer device, for exampleas done when performing digital audio extraction (also known as ripping)of musical content from an audio CD. The apparatus and method of thepresent invention permit improved control of the usage and copying ofpublished content on physical media by an immediate purchaser whilelimiting copying and distribution of the content to unauthorizedrecipients.

Individuals commonly use a recording drive connected to a personalcomputer to record audio CDs (this process is also known as burningCDs). So-called burning software, such as sold by Adaptec and othercompanies, is used to control the computer during the CD burningprocess. The recorded CDs may be made using standard CD-R and CD-RWrecordable storage mediums.

Individuals typically use such recorded CDs to create compilations ofmusic that may be obtained from multiple different sources. Such sourcesinclude audio CDs purchased by the individual, MP3 music filesdownloaded from the Internet, and digital music files using otherstandard formats. These sources may further include music files obtainedunder a digital rights management (DRM) system. For example, anindividual may purchase several audio CDs and then record selected musictracks from each CD to a newly created compilation CD-R.

A problem with existing CD burning software is that the audio CDscreated can be distributed to other individuals who can use thenewly-created CD to create yet other audio CDs or additional digitalcopies of the music content on the CD. Further, existing CD burningsoftware does not use a copy protection mechanism to control the useand/or subsequent copying of such content. In many cases, theindividuals receiving a newly-created CD from an original purchaser ofthe source CD will not be authorized or otherwise have the right to makeor distribute copies of the music content. However, audio CDs made usingexisting burning software will permit unauthorized individuals to use anewly-created CD to upload the music content to an Internet server orother computer for public distribution or to create additional audio CDsthat may be improperly distributed.

The music and other entertainment industries have a business interest inpromoting sales of CDs and other storage medium containing entertainmentcontent. However, the music and entertainment industries desire tocontrol the burning and handling of CDs by customers in a way thatrestricts unauthorized distribution to others who have not purchased oracquired a right from the publisher to receive entertainment content.

Thus, there is a need for an audio CD recording system that permitsaudio CD consumers to make compilation CDs for personal use, but thatcontrols or prevents the unauthorized uploading to the Internet ormaking of subsequent CD copies using the compilation or other audio CDrecorded by the consumer without requiring hardware modifications ormodification of the actual data content itself There is a further needfor compilation CDs made using this audio CD recording system to retainfull playability in audio CD players in order to meet current consumerexpectations regarding the use of purchased audio CDs and audio CDsburned from these purchased CDs.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a compact disc recording systemaccording to the present invention;

FIG. 2 illustrates the contents of a multiple session compact discrecorded using the recording system of FIG. 1;

FIG. 3 is a flow diagram illustrating a recording method for a storagemedium using digital content concealment according to the presentinvention;

FIG. 4 illustrates the standard subcode structure for audio CDs;

FIG. 5 illustrates the standard channel Q data format for the subcodestructure of FIG. 4;

FIG. 6 illustrates the standard mode I Data-Q lead-in track format forthe channel Q data format of FIG. 5;

FIG. 7 illustrates the standard mode I Data-Q audio and lead-out trackformat for the channel Q data format of FIG. 5;

FIG. 8 is a table illustrating an example of a table of contents (TOC)according to the present invention for a first session of a CD;

FIG. 9 is a table illustrating an example of a table of contentsaccording to the present invention for a second session of a CD; and

FIG. 10 is a table illustrating an example of modified CRC values in thechannel Q data of the program area of a CD according to the presentinvention.

FIG. 11 is a table illustrating an example of modified ATime values inthe channel Q data of the program area of a CD according to the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides an apparatus and method for concealingdigital content on a physical medium such as, for example, a CD that isrecorded using a computer recording system and that permits improvedcontrol over the copying and distribution of the content stored on theCD. In a specific embodiment, the recording system according to thepresent invention permits an individual to use a personal computer toburn a first audio CD that incorporates copy protection and to preventfurther copying of the music content from that CD. By preventing furthercopying, the burned CD cannot be used as an improper source of music tobe uploaded to, for example, the Internet or for use in burningadditional CDs. The present invention is discussed below in thenon-limiting example of an audio CD, but may be generally used withother types of digital storage media including, for example, CD-ROMs andDVDs. Accordingly, the present invention extends to and is useful withthese other media.

According to the present invention, digital content on a CD recordedusing the recording system as described herein is concealed by makingmodifications to the control data that is located in the so-called“lead-in area” and stored along with the audio content on the CD.Modifications are also made to certain error checking and timing valuesthat are located in the so-called “program area” and used torespectively verify a lack of errors in the associated control data andprovide timing information. These modifications are discussed in moredetail below.

In addition, according to the present invention, the recorded CD is alsomade into a multiple session CD having first and second sessions inwhich the first session actually contains audio data, but is coded toindicate that it contains digital data, and has intentional errorsintroduced to its control data as described below. The second sessioncontains digital data in a standard format, which may include, forexample, data identifying the creation date or source of thenewly-burned CD or an HTML file that contains information and/or a URLassociated with a music publisher or distributor or an artist. When aburned CD created according to the present invention is placed into apersonal computer, the first session, and hence the audio content, isnot readable by the computer. Instead, the computer may displayinformation to the user corresponding to the data stored in the secondsession or launch a computer program stored in the second session. Theforegoing and other aspects of the present invention are discussed inmore detail below.

FIG. 1 is a compact disc recording system 100 according to the presentinvention and includes a computer 101 connected to or incorporating a CDrecording drive 102. Computer 101 may be a personal computer such as,for example, a MICROSOFT WINDOWS and INTEL-based machine. Othercomputers may also be used as will be recognized by one of skill in theart. Recording drive 102 is, for example, a CD-R or CD-RW drive that iscapable of recording or burning standard CDs. To use the digital contentconcealment approach as described below, recording drive 102 must becapable of supporting so-called raw mode burning due to the need toencode data into the subcode structure of CD 106.

Recording software 104 runs on computer 101 and controls computer 101and drive 102 to create a recorded compact disc 106. Recording software104 may be programmed in C++or other conventional computer languages toimplement the functionality and digital concealment approach asdescribed further below. Recording software 104 may also be written as aso-called “plug-in” to work in conjunction with a media player such as,for example, Microsoft Corporation's WINDOWS MEDIA PLAYER. Recordingsoftware 104 may, for example, provide options for selection by the userof the burning speed, selection of the files (stored on computer 101) tobe burned to CD 106, and an interface that indicates the percentagecomplete or progress of the burning operation.

The source of content to be recorded on CD 106 may include, for example,music from standard audio CD 108, MP3 files 110 downloaded to computer101 from the Internet, and Digital Rights Management (DRM) files 112.These and other sources of music can be used with the present invention.In general, music from each source is conventionally converted to a WAVformat prior to burning CD 106. Optionally, the source of content couldcontain a flag that is readable by recording software 104 and thatinstructs recording software 104 regarding the specific manner or formof digital concealment that recording software 104 incorporates into CD106.

Compact disc manufacturing and production technology is establishedaccording to a series of international publications, herein referred toas “standards”, all of which are incorporated herein by reference as ifset forth fully herein. For example, some common standards applicable toCDs include: the International Standards Organization (ISO) standard9660 entitled “Information Processing—Volume and File Structure ofCD-ROM for Information Interchange, ISO Standard 13490-1”, theInternational Electrotechnique Commission (CEI-IEC) standard 908, alsoknown as the “Red Book”, and ISO/IEC 10149, also known as the “YellowBook”.

FIG. 2 illustrates the contents 200 of a multiple session compact disc,for example CD 106, recorded according to the present invention. CD 106contains contents 200. As mentioned above, according to the presentinvention, contents 200 corresponds to a multiple session CD havingsessions indicated as SESSION 1 and SESSION 2 in FIG. 2.

SESSION 1 contains a lead-in area 202, a program area 204, and alead-out area 206. Program area 204 contains data tracks containingaudio music content 214, and lead-in area 202 contains a table ofcontents 212 corresponding to these data tracks. Lead-out area 206 actsas a spacer between sessions and indicates the location of SESSION 2 onCD 106. The storage format of the digital content in SESSION 1 conformsto industry standards except as discussed herein. Certain modifications(discussed below) are made to control values associated with table ofcontents 212. These modifications include the addition of extra entriesin the TOC for each track beyond the 3 instances defined by thestandard. These modifications further include identifying SESSION 1 asdigital data in the first number of valid TOC entries, and as audio datain the remaining instances, even though SESSION 1 actually containsaudio data tracks in program area 204. Alternate variations ofidentifying each TOC entry as data or audio shall fall within thispresent invention. Certain other modifications (also discussed below)are made to error checking and timing values associated with controlinformation stored with music content 214.

SESSION 2 contains a lead-in area 208 and a user data area 210containing digital data. The storage format of the digital content inSESSION 2 conforms to industry standards for digital data sessions, andin particular, the data stored in user data area 210 conforms to the ISO9660 standard for CD-ROM data storage. User data area 210 contains aninformation file or computer program, for example, that is automaticallyread by the operating system when computer 101 reads SESSION 2.

In other embodiments, SESSION 2 could contain MP3 files that correspondto the audio tracks stored in SESSION 1. Thus, if a music publisherincorporated digital content concealment as described below into anoriginal audio CD purchased by a consumer, then the consumer could stillburn the audio CD for personal use. This could be accomplished byprogramming recording software 104 to recognize a flag placed by a musicpublisher on the original audio CD that directs the use of SESSION 2 asthe music source. Alternatively, recording software 104 canautomatically obtain source music content from SESSION 2 in the eventthat data cannot be read from SESSION 1 due to use of the digitalcontent concealment approach described below.

According to the present invention, when CD 106, recorded as describedherein, is mounted in a CD-ROM drive of a digital computer (not shown),audio music content 214 cannot be read by the digital computer becausethe control data of SESSION 1 has intentional errors introduced by thecurrent invention such as, for example, the identification of SESSION 1as digital data and other errors as more fully described below. When thedigital computer attempts to read program area 204 as digital data, thedigital computer aborts reading the data because the audio content inprogram area 204 does not conform to the ISO 9660 data standard.

Because CD 106 is a multiple session CD, after the digital computeraborts the attempt to read SESSION 1, the digital computer next attemptsto read SESSION 2 (as is standard) and successfully reads theinformation stored in user data area 210, which contains, for example,an information file or a computer program that may be automaticallylaunched by the digital computer.

FIG. 3 is a flow diagram illustrating the digital content concealmentand authorized distribution method according to the present invention.In step 400, a first audio session of multiple session CD 106 iscreated. In step 402, lead-in area 202 is modified to identify the firstsession as containing data.

In step 404, selected control values in table of contents 212 are set tonon-standard values (as discussed below). In step 406, selected errorchecking values in program area 204 are modified to non-standard values.The modifications of steps 404 and 406 are done to conceal or preventreading of musical content 214 by personal computers and other types ofCD copiers and readers.

In step 408, a second session of CD 106 is created. In step 410, an HTMLfile or other data or identification information and/or a computerprogram are stored in user data area 210. The identification informationcould, for example, be used to identify the version or type of recordingsoftware 104 used to burn CD 106, or provide other information about thenature of the source of the music recorded onto CD 106.

FIG. 4 illustrates the subcode structure 500 according to the standardsfor audio CDs. In general, data is stored on an audio CD in standardso-called “frames” in program area 204, where each single framecorresponds to 1/75^(th) of a second of playing time. Each framecontains the audio content for that time period and also containsadditional control and error checking information stored in a portion ofthe same frame. The control information is split into 8 channels 502(indicated by the letters P, Q, R, S, T, U, V, and W) as defined in thestandards such as, for example, in the Red Book.

The channels are stored in the frame in an interleaved manner accordingto the standards in so-called 98 small frames indicated as 0, 1, 2 . . .97 at reference number 506. Small frames 0 and 1 are reserved by thestandards for sync patterns S0 and S1 (indicated by reference number508), which are only used internally within the CD player hardware anddo not store any actual channel data. The remaining 96 small frames eachstore 1 bit of channel data, indicated as bits d1 . . . d8 (indicated byreference number 504) so that each channel stores 96 bits per frame.These 96 bits are indicated for the Q channel by reference number 512.Each of small frames 506 in subcode structure 500 contains 8 bits (toform a single control byte in the interleaved frame structure mentionedabove), and each frame contains a total of 96 such control channelbytes.

Frames are also used to store data in lead-in area 202. Table ofcontents 212 is typically stored in the Q channel of each frame oflead-in area 202, and the audio content of each frame in the lead-inarea is typically zero.

FIG. 5 illustrates the standard channel Q logical data format 600 forsubcode structure 500. As mentioned above, the Q channel for each framestores 96 bits of data, which is structured as indicated in data format600. Fields 602 and 612 correspond to the standard sync patternsmentioned above and are not part of the Q channel data.

The Q channel data is structured into fields 604, 606, 608, and 610.Field 604 is a control field that defines, among other things, whetherdata in the program area of a CD is audio or digital data. Field 606 isan address field that indicates the mode for a subset of format 600(discussed below). Field 608 contains the data bits for the Q channel,and field 610 contains error checking values, which are implemented inthe standards as a cyclical redundancy check (CRC) on the control,address, and data fields 604, 606, and 608.

FIG. 6 illustrates the standard mode 1 Data-Q lead-in track format 700for the channel Q data format 600 of FIG. 5. The format in FIG. 6 isused to store the information for table of contents 212 on CD 106. Byindustry practice, audio CDs typically use standard mode 1 as the valuefor address field 606 in lead-in area 202, indicated by a value of 1 inthe ADR field of FIG. 6. The fields corresponding to DATA-Q field 608are standard fields 702-718 as defined in the standards. The TNO fieldis set by the standards to zero for all records in table of contents212.

FIG. 7 illustrates the standard mode 1 Data-Q audio and lead-out trackformat 800 for the channel Q data format 600 of FIG. 5. The format inFIG. 7 is used to store the channel Q data for music content 214 inprogram area 204. By industry practice, audio CDs also use standard modeI as the value for address field 606 in the program and lead-out areas204 and 206. The fields corresponding to DATA-Q field 608 for audio andlead-out track data are standard fields 802-818 as defined in thestandards.

FIG. 8 is a table 900 illustrating an example according to the presentinvention of table of contents 212 for SESSION 1 of CD 106. Table 900 isa simplified version of the data in an actual table of contents, whichaccording to the standards has each record repeated three times and theentire set of records repeated several times throughout lead-in area202. Each record (or row) in table 900 corresponds to a single frame or1/75^(th) second of lead-in running time on CD 106.

Column 904 of table 900 contains values in hexadecimal form thatcorrespond to the values of the 8 bits contained in control and addressfields 604 and 606 of FIGS. 5-7. Table 900 also contains thecorresponding exemplary values for standard fields 702-718 of the Qchannel data format.

According to the present invention, the control/address (also referredto herein as “control”) values in column 904 are set in non-standardways to conceal music content 214. For those frames in which the POINTfield has a value between 1 and 99, which corresponds to a track number,the control/address byte in column 904 is set to 41h. This valueidentifies the record as a mode 1 record and identifies CD 106 as havingdigital data in program area 204. It should be recalled that thecontents of program area 204 are actually recorded as standard audiodata. Identifying the track data as digital data prevents program area204 from being read by substantially most personal computers and alsoprevents digital audio extraction using substantially most of thehardware and software currently available for such purpose including,for example, most ripping software programs. The concealment of thedigital audio content is accomplished because computers and rippingsoftware usually check the table of contents to determine the locationof the audio content on CD 106 (i.e., the starting and ending points ofthe data tracks). Because the table of contents identifies some numberof tracks as being digital data, most computers and ripping software donot operate to extract and/or play music content 214 from CD 106.Computers and ripping software that bypass the table of contents andattempt to read the program area 204 as audio will generally experienceproblems extracting the digital audio content due to the intentionalerrors introduced to the program area 204 during the recording process.According to the present invention, the table of contents 212 errors andprogram area 204 errors need not be incorporated on a CD simultaneouslybut may be incorporated individually while still obtaining a desirablelevel of copy protection.

Although computers in general are not able to read content from programarea 204, audio CD players are able to play music content 214 fromprogram area 204 because such players do not check the control valuesstored in table of contents 212 and because such players are generallyaccustomed to handling errors introduced into the program area 204 ofthe CD. Thus, such audio players are not affected by the identifying ofstored content as data content rather than as audio content, nor of theintroduction of errors into the program area 204.

For those frames in which the POINT field is equal to the standardvalues of A0, A1, and A2 (which correspond to a specific standard typeof table of contents information relating to the location of the firstand last data tracks and the lead-out), the control/address byte is setto a hexadecimal value of 21 (indicated as 21h). This value identifiesthe record as a mode 1 record and CD 106 as having audio data in theprogram area. This value is selected to be different from the controlvalue of 41h for those frames in which the POINT field has a tracknumber value so that the control byte value is changed more frequentlythan is permitted under the standards. As a result, some computersystems such as, for example, an APPLE MACINTOSH computer operatingunder the MAC OS 9.0 operating system, will not read music content 214from program area 204. This occurs because the MAC OS 9.0 operatingsystem expects table of contents 212 to be compliant with the Red Bookstandards. According to the standards, the control byte value, ifchanged, must last at least 2 seconds, which corresponds to 150 frames.

The last two rows of table 900 have the control/address byte set to 05h.This corresponds to a standard control byte used to indicate that CD 106is a multiple session CD, which corresponds to a so-called mode 5 underthe standards. Specifically, these two mode 5 records are used toidentify the starting time of the lead-in areas for each of the firstand second sessions of CD 106.

FIG. 9 is a table 1000 illustrating an example according to the presentinvention of a table of contents for SESSION 2 of CD 106. Lead-in area208 uses the Q channel to store table of contents information similarlyas discussed above for SESSION 1. Table 1000 is a simplified version ofthe data in the actual table of contents, as discussed above for FIG. 8.The presence of SESSION 2 on CD 106 aids in the prevention of digitalaudio extraction because some ripping software programs do not operateon multiple session CDs.

Column 1004 of table 1000 contains values in hexadecimal form thatcorrespond to the values of the 8 bits contained in control and addressfields 604 and 606 of FIGS. 5-7. Table 1000 also contains thecorresponding exemplary values for standard fields 702-718 of the Qchannel data format discussed above.

According to the present invention, the control bytes in column 1004 areset to a value of 41h to indicate that the record is a mode 1 record inthe Q channel and that user data area 210 contains digital data storedaccording to the ISO 9660 standards. The control value of 41 hcorresponds correctly to the type of data stored in SESSION 2. When CD106 is placed into a CD-ROM drive of a digital computer, as discussedabove, it encounters a read error when attempting to read SESSION 1 andnext attempts to read SESSION 2 according to, the standards. However,the CD-ROM drive is able to normally read the digital data from SESSION2.

FIG. 10 is a table 1100 illustrating an example of modified CRC valuesin the channel Q data of program area 204 of CD 106. According to thepresent invention, in addition to the modifications made to the controlvalues as discussed above, changes are also made to the error checkingvalues, implemented here in the Q channel as CRC values in field 610(see FIG. 5). In general, a certain proportion of the CRC values for theaudio content in program area 204 of SESSION 1 are modified toperiodically repeat throughout program area 204 as discussed in moredetail below. These modifications are made beginning 5 seconds into eachtrack of program area 204 and continuing throughout all frames ofsubject track, and repeating in a similar manner for every track in userprogram 204.

Column 1102 of table 1100 lists exemplary frame addresses in hexadecimalformat starting with address 00. For purposes of illustration, thestarting logical block address for the first frame is 00, but it shouldbe appreciated that the actual first frame in the program area 204typically corresponds to the beginning of a standard period of silence(typically having a duration of two seconds and known as “pre-gaps”)immediately following the frames for the table of contents and has alogical block address of, for example, FFFFFF6Ah. According to thepresent invention, modified CRC values are used starting with the firstframe residing 5 seconds into each track from the beginning of the 2second “pre-gap” and continuing throughout the audio track, and thenrepeated for each track in the program area.

Column 1104 indicates the CRC value stored onto CD 106 for each frame inprogram area 204. According to the present invention, a set number ofinitial frames in each period of frames is intentionally set to aninaccurate value, here shown, for example, as FFFFh, which does notaccurately correspond to the DATA-Q values stored in field 608 (see FIG.5). Inaccurate CRC values other than FFFFh could also be selected.

Column 1104 illustrates a frame period 1110 of every 13 frames with thefirst four frames 1106 of each period set to an inaccurate FFFFh value.The other 9 frames 1108 are set to accurate CRC values according to thestandards.

Other variations could be made to the particular inaccurate CRC patternused according to the invention. For example, the period could bechanged to be greater than 13 frames such as, for example, 75 or 150frames. Also, the proportion of inaccurate CRC values within each periodcould be increased or decreased. Further, the inaccurate CRC valuescould be scattered throughout each period rather than being located in asingle group of consecutive frame addresses.

FIG. 11 is a table 1200 illustrating an example of modified ATime valuesin the channel Q data of program area 204 of CD 106. According to thepresent invention, in addition to the modifications made to the controlvalues as discussed above, changes are also made to the ATime values,implemented here in the Q channel as ATime errors in fields 814 and 816(see FIG. 8). In general, a certain proportion of the ATime values forthe audio content in program area 204 of SESSION 1 are modified toperiodically repeat throughout program area 204 as discussed in moredetail below. These modifications are made beginning at either 3 or 5seconds into each track, depending on the type of modification, ofprogram area 204 and continuing throughout all frames of subject track,and repeating in a similar manner for every track in user program 204.

Column 1202 of table 1200 lists exemplary frame addresses in hexadecimalformat starting with address 00. For purposes of illustration, thestarting logical block address for the first frame is 00, but it shouldbe appreciated that the actual first frame in the program area 204typically corresponds to the beginning of a standard period of silence(typically having a duration of two seconds and known as “pre-gaps”)plus some delay (typically having a duration of 3 or 5 seconds)immediately following the frames for the table of contents and has alogical block address of, for example, FFFFFF6Ah. According to thepresent invention, modified ATime values are used starting with thefirst frame of this period of silence plus the delay and continuingthroughout each audio track and repeating in a similar manner for everytrack in user program 204.

Column 1104 indicates the CRC value stored onto CD 106 for each frame inprogram area 204. According to the present invention, a set number offrames in each period of frames is intentionally set to an inaccuratevalue, here shown, for example, as being one frame less than it shouldbe, which does not accurately correspond to the actual ATime values.Inaccuracies in the ATime values greater than 1 frame could also beselected.

Column 1204 illustrates a frame period 1210 of every 65 frames such thatframes 11, 23, 35 and 47 1206 each have ATime values which are 1 frameless than it should be starting 5 seconds after the start of the pregap(assuming a pregap of 2 seconds in length). Column 1204 furtherillustrates a frame period 1210 of every 65 frames such that frames 1-4,6-9, 11-14 1207 each have ATime values which are 1 frame more than itshould be starting 3 seconds after the start of the pregap (assuming apregap of 2 seconds in length). The other frames 1208 are set toaccurate ATime values according to the standards. Inaccuracies couldhave been introduced into frames other than frames 11, 23, 35, and 47.

Other variations could be made to the particular inaccurate ATimepattern used according to the invention. For example, the period couldbe changed to be greater than 65 frames such as, for example, 95 or 130frames. Also, the proportion of inaccurate ATime values within eachperiod could be increased or decreased. Further, the inaccurate ATimevalues could be scattered differently throughout each period rather thanbeing located where currently illustrated.

It has been found that most computers and digital audio extractionsoftware such as ripping software will not operate to extract audio datafrom CD 106 when the periodic CRC errors or ATime errors described aboveare present. However, it has been learned that substantially most CDaudio players, including shock resistant models, will still play musiccontent 214 from program area 204 even though it contains periodic CRCerrors. Most such audio players calculate a CRC value during play andcompare it to the CRC value of column 1104. Such audio players aredesigned to tolerate a certain minimal number of CRC errors and continueplaying. It has been found that modifications to the CRC in the firstfour frames of every 13 frames is tolerated by most such audio players.Furthermore, it has been determined that modifications to the ATime incertain frames are similarly tolerated by most such audio players.

The selection of the period and number of bad CRC and ATime values usedin each period is a process of balancing playability on audio CD playersagainst preventing computers and digital audio extraction software frombeing able to extract audio content. In other words, it is desired thatthe proportion of frames with inaccurate CRC be high to defeat rippingsoftware, without being so high that audio CD players are unable to playthe audio content.

The CRC modifications described above could also be made to lead-outarea 206, but this is not necessary to accomplish the benefits of thepresent invention. Lead-in area 202 and all of SESSION 2 do not have theabove CRC modifications made.

By the foregoing description, a novel recording system apparatus andmethod for the recording of CDs with burning software that provides theconcealment of digital content on the CD have been disclosed. Thepresent invention has the advantages of protecting published content onburned CDs from unauthorized distribution while providing, for example,the original purchaser of an audio CD with the ability to create apersonal compilation CD. Further, the recording system according to thepresent invention is in alignment with the business interests of themusic industry.

The use of the present recording system permits publishers to offer abroader range of audio and video material at lower prices due to areduction in the loss of profits that might otherwise occur due tounauthorized distribution and pirating. Further, CDs produced accordingto the present invention are playable in most audio CD players,including shock resistant types, but are not playable in most computersystems and thus cannot be duplicated by ripping software or othersoftware programs using digital audio extraction. Moreover, according tothe present invention, the audio music content is not modified and isinstead identical to that available from the type of source music usedduring recording, whether such type is an audio CD, MP3 file, or othertype. Accordingly, there is no audio playback degradation relative tothe original source when the CD is played on audio players.

In addition to the above advantages, there are other advantages providedto individual computer users. For example, individual consumers orsmaller musical arts companies can use the recording system on apersonal computer and the method of the present invention to protect CDsthat are created for providing to music publishers or others as samplesor for CDs that are sold or otherwise provided to customers directly bysuch individuals or companies.

Although specific embodiments have been described above, it will beappreciated that numerous modifications and substitutions of theinvention may be made. For example, the present invention may be appliedto other types of formats such as, for example, CD-ROM, CD-R, CD-i,DVD-A, and CDR-G formats. Accordingly, the invention has been describedby way of illustration rather than limitation.

1. A system for concealing digital content on a physical medium,comprising: a personal computer, said personal computer comprisinghardware and software that is constructed and arranged to permit aconsumer to bum an optical disc; and wherein at least one of saidhardware and said software is configured so as to enable the consumer tobum an optical disc that incorporates copy protection.
 2. A systemaccording to claim 1, wherein said copy protection is configured so asto permit improved control over the copying and distribution of contentthat is stored on the optical disc.
 3. A system according to claim 1,wherein said copy protection is configured to frustrate further copyingof the content from the optical disc.
 4. A system according to claim 1,wherein said optical disc comprises a CD, and wherein said copyprotection incorporates means for making modifications to control datathat is located in a lead-in area of the CD.
 5. A system according toclaim 1, wherein said optical disc comprises a CD, and wherein said copyprotection incorporates means for verifying a lack of errors in controldata on the CD.
 6. A system according to claim 1, wherein at least oneof said hardware and said software is configured so as to enable theconsumer to make a multiple session CD having first and second sessionsin which the first session actually contains audio data, but is coded toindicate that it contains digital data, and has intentional errorsintroduced to its control data.
 7. A system according to claim 6,wherein said second session contains digital data in a standard format.8. A system according to claim 1, wherein at least one of said hardwareand said software is configured so as to enable the consumer to bum amultisession optical disc.
 9. A system according to claim 8, wherein atleast one of said hardware and said software is configured so as toenable the consumer to burn a multisession optical disc comprising afirst session containing content in a first file format and a secondsession containing the same content in a second file format.
 10. Asystem according to claim 8, wherein at least one of said hardware andsaid software is further configured so as to enable the consumer to buma computer program on to the optical disc.
 11. A system according toclaim 9, wherein at least one of said hardware and said software isfurther configured to bum information on said multisession optical discthat relates to the copy protected status of the content.
 12. A systemaccording to claim 1 1, wherein at least one of said hardware and saidsoftware is further configured to bum information on to saidmultisession optical disc that will instruct a personal computer as tothe specific form of copy protection that has been applied to theoptical disc.
 13. A personal computer, comprising: accessing means foraccessing a digital work; determining means for determining whether saiddigital work is copy protected; and recording means for recording a copyprotected digital work on to a portable digital media in a copyprotected format.
 14. A personal computer according to claim 13, whereinsaid accessing means comprises an optical disc reader for accessing saiddigital work from an optical disc.
 15. A personal computer according toclaim 14, wherein said determining means comprises a program that runson said personal computer, and wherein said program is constructed andarranged to receive copy protection information that is encoded on saidoptical disc.
 16. A personal computer according to claim 15, whereinsaid recording means is constructed and arranged to record said copyprotected digital work on to an optical disc together with said encodedcopy protection information.
 17. A personal computer according to claim13, wherein said recording means comprises an optical disc recorder thatis constructed and arranged to record said digital work in a firstformat on a first session of an optical disc and to further record saiddigital work in a second format on a second session of said opticaldisc.
 18. A personal computer according to claim 17, wherein saidrecording means is further constructed and arranged to record encodedcopy protection information on said optical disc.
 19. A copy protectedoptical disc, comprising: a digital work recorded on said optical discin a copy protected format; and information encoded on said optical discfor a personal computer relating to copying of said digital work by saidpersonal computer on to a recordable optical disc in a copy protectedformat.
 20. A copy protected optical disc according to claim 19, furthercomprising a computer program recorded on said optical disc that may beexecuted by the personal computer.
 21. A method of distributing digitalcontent, comprising: providing the digital content to a consumer in acopy protected format; and enabling the consumer to record the digitalcontent on to an optical disc in a copy protected format that will limitfurther dissemination of the digital content.
 22. A method ofdistributing digital content according to claim 21, wherein said step ofenabling the consumer to record the digital content comprises providingrecording software that is executable on a personal computer forpermitting recordation of the digital content on to an optical disc in acopy protected format.
 23. A method of distributing digital contentaccording to claim 22, wherein said recording software permits thedigital content to be recorded in a first file format on a first sessionof the optical disc and in a second, different file format on a secondsession of the optical disc, and wherein said recording software isfurther constructed and arranged to record information on to the opticaldisc relating to the nature of the copy protection.